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#1
posted to rec.boats.building
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Strip Planking Hull Thickness
Hello all,
Can anyone assist me with the calculation for strip planking hull thickness...? We are embarking on a build of a 40ft ketch. I know there is Dave Gerr's formulae for determining this but have not got his book (not available in SA). I intend exoxy glass in/out. Also, what influence will a different wood species make on the thickness required? ie: mahogany vss cedar vss ... vss ... Thanks for the info - cheers, Max |
#2
posted to rec.boats.building
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Strip Planking Hull Thickness
Goo'day, Max
On Thu, 26 Oct 2006 08:23:22 +0200, Max Hazelhurst wrote: Hello all, Can anyone assist me with the calculation for strip planking hull thickness...? Very briefly, the result of the calculation is whatever the designer specifies. No designer? You're the designer? Oh dear..... Might I suggest you start your career with a slightly less ambitious project? About 30' less.... Regards, Bruce Nichol ALBURY NSW Australia |
#3
posted to rec.boats.building
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Strip Planking Hull Thickness
Max Hazelhurst wrote:
Can anyone assist me with the calculation for strip planking hull thickness...? We are embarking on a build of a 40ft ketch. Sounds like a large project to begin with. I know there is Dave Gerr's formulae for determining this but have not got his book (not available in SA). I intend exoxy glass in/out. Well, do get that book. It is available from on-line dealers that ship around the world. Gerr does give neat and simple formulas, but there too many factors to cover in a newsgroup post. Get that book! I think Herreshoff also published his scantling rules, but watch out, those were lighter, and assumed more qualified woodworking. Chapelle might have published scantling rules too, I don't remember. Larsson's and Eliasson's "Principles of Yacht Design" is a good modenr work that will tell you a lot. I know getting these books takes time and trouble. Reading and understanding even more so. I bet that time more than pays itself when you finally start building. And if you get your boat to sail, you sleep much better if you *know* that the construction is solid enough for your waters. If you are asking that kind of questions, I recommend a year of reading, and then a year or three of designing, before you start to chop wood... When you get to the concrete questions, ask again. I'm sure this group can help with many details. Good luck with the project! - Heikki (already at the design stage, for a 24' schooner) |
#4
posted to rec.boats.building
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Strip Planking Hull Thickness
Hi all,
cool - thanks for the heads-up thusfar. I'll organize the book via the UK and take it from there. I have spec's to work against for the plans that I am working off - being the inquisitive sort, I want to understand the dynamics behind this and also investigate some alternative species that I may have access to here in S.Africa. I'll post my findings here for reference and comment. Thanks, M |
#5
posted to rec.boats.building
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Strip Planking Hull Thickness
It depends on the type of wood and the layup schedule of the glass. It
really needs to be vary carefully analyzed and balanced. On my 45' hull the designer called for 1.125" thick by 1.75" wide white cedar with 4 layers of unidirectional diagonally laid below the waterline and 2 layers above with 2 layers on the inside plus some Kevlar in the forward slamming areas. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com "Max Hazelhurst" wrote in message ... Hello all, Can anyone assist me with the calculation for strip planking hull thickness...? We are embarking on a build of a 40ft ketch. I know there is Dave Gerr's formulae for determining this but have not got his book (not available in SA). I intend exoxy glass in/out. Also, what influence will a different wood species make on the thickness required? ie: mahogany vss cedar vss ... vss ... Thanks for the info - cheers, Max |
#6
posted to rec.boats.building
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Strip Planking Hull Thickness
Hi Glenn,
Thanks - I've looked quite a bit at your site in the past so, appreciate the work that I'm throwing myself into... Thanks for the info - I'll get the specifications hopefully quite soon from the designers and post for comment and possible concerns. Thanks Max |
#7
posted to rec.boats.building
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Strip Planking Hull Thickness
Max,
I am also building a 40ft. ketch. It's not intended to be 'light' displacement, and has a D/L ration of 230. It is intended to be structurally perhaps a bit lighter than the traditional construction plans I started with. For strip-plank with no ribs, except at bulkheads, Bill Garden advised 1 3/8" strips. For the same with no ribs (except bulkheads) and sheathed in and out with 30 oz. glass, Tom MacNaughton advised 1 inch. I suggest you get "Sheathed Strip Construction Scantlings Rule" from MacNaughton Associates, Inc., Eastport Boat Yard and Supply, Box 190, Eastport, Maine 04631, USA. I hope that address is still good. I bought the rule about 10 yrs. ago. At that time his phone was 207-853-6049. He has a rule that easily sets up in a spreadsheet and is based on displacement. It's designed to build boats at least as strong as per Nevin's rule, and often lighter. Remember that with strip planking you need something to add cross-grain strength. That can either be ribs or sheathing. I compromised. My hull has several bulkheads, each with a rib. It has one rib between each pair of bulkheads so it's not fully ribbed. It has MacNaughton's 30 oz. exterior sheathing but only 10 oz. interior, figuring I'd get the extra strength from the ribs I have, and allows me to finish the interior bright. I planked with 1 7/16" square strips. My planking thickness, after fairing, is probably 1 3/8" max, less in some areas depending on how much fairing was needed. Max Hazelhurst wrote: Hello all, Can anyone assist me with the calculation for strip planking hull thickness...? We are embarking on a build of a 40ft ketch. Max |
#8
posted to rec.boats.building
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Strip Planking Hull Thickness
Hi there,
Awesome - that's really helpful - I found Tom's website and have emailed him about the scantlings rule book. Do you have any photo's of your build - especially the ribs/bulkhead/inner hull areas? You can email me off-list: maxh ..@.. zelhurst...com Thanks, Max Max, I am also building a 40ft. ketch. It's not intended to be 'light' displacement, and has a D/L ration of 230. It is intended to be structurally perhaps a bit lighter than the traditional construction plans I started with. For strip-plank with no ribs, except at bulkheads, Bill Garden advised 1 3/8" strips. For the same with no ribs (except bulkheads) and sheathed in and out with 30 oz. glass, Tom MacNaughton advised 1 inch. I suggest you get "Sheathed Strip Construction Scantlings Rule" from MacNaughton Associates, Inc., Eastport Boat Yard and Supply, Box 190, Eastport, Maine 04631, USA. I hope that address is still good. I bought the rule about 10 yrs. ago. At that time his phone was 207-853-6049. He has a rule that easily sets up in a spreadsheet and is based on displacement. It's designed to build boats at least as strong as per Nevin's rule, and often lighter. Remember that with strip planking you need something to add cross-grain strength. That can either be ribs or sheathing. I compromised. My hull has several bulkheads, each with a rib. It has one rib between each pair of bulkheads so it's not fully ribbed. It has MacNaughton's 30 oz. exterior sheathing but only 10 oz. interior, figuring I'd get the extra strength from the ribs I have, and allows me to finish the interior bright. I planked with 1 7/16" square strips. My planking thickness, after fairing, is probably 1 3/8" max, less in some areas depending on how much fairing was needed. Max Hazelhurst wrote: Hello all, Can anyone assist me with the calculation for strip planking hull thickness...? We are embarking on a build of a 40ft ketch. Max |
#9
posted to rec.boats.building
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Strip Planking Hull Thickness
On Thu, 26 Oct 2006 08:23:22 +0200, Max Hazelhurst
wrote: Also, what influence will a different wood species make on the thickness required? ie: mahogany vss cedar vss ... vss ... Mahogany would not be my first choice since it is much less rot resistant than cedar as I understand it. |
#10
posted to rec.boats.building
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Strip Planking Hull Thickness
Mahogany is also a lot heavier than cedar and not as tolerant to bending.
Strip composite uses the strips as a core and its strength depends on the core maintaining its shear strength. Cedar can absorb more deflection from pounding. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com "Wayne.B" wrote in message ... On Thu, 26 Oct 2006 08:23:22 +0200, Max Hazelhurst wrote: Also, what influence will a different wood species make on the thickness required? ie: mahogany vss cedar vss ... vss ... Mahogany would not be my first choice since it is much less rot resistant than cedar as I understand it. |
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